Every circumstance is different and should be handled differently. If some dude rolls up in the mall (or wherever) and starts shooting random people, it's a pretty safe bet he's the bad guy. But that's only one exceedingly rare scenario among thousands of other more likely ones. You may have to make snap decisions in the unfortunate event that you're ever caught up in a deadly force situation, but the mindset that going in guns blazing is always the right call is immature and dangerous.